[50.04] Mapping the HI Distribution in the Leo I Group

Using a wide-field radio survey we determined the HI mass
distribution in Leo I, a low-density group of galaxies
located at a distance of 10 Mpc. HI spectral line data were
collected using the L-narrow receiver of the Arecibo Radio
telescope. The telescope was operated in scanning mode in
order to completely map a 3 \arcdeg \times 3 \arcdeg
section of sky, matching that covered by a deep optical
survey by Flint et al. (2001, ApJS, 134, 53). The survey is
sensitive over the velocity range 0 < v < 5000 km/s to a
low-mass limit of 1.1 \times 107 M\sun at a distance
of 10 Mpc. The advantage of conducting this type of blind
survey is that it will detect all the galaxies present down
to the HI mass limit rather than being biased toward
optically bright galaxies.

Apart from the two large spiral galaxies, NGC3368 and
NGC3351, most of the HI detections found by the survey were
associated with a known HI ring in the group's core. None of
the dwarf galaxies in Leo I had sufficient HI gas to be
detected by our survey, which suggests that the HI mass
function of Leo I may exhibit a lack of intermediate mass
objects similar to the observed gap in the luminosity
function between -19.5 < MR < -16 (Flint et al. 2003,
Ap&SS, 285, 191). No galaxies were detected in HI which had
not been previously detected optically, which suggests that
there are no gas-rich dark-matter dominated galaxies present
in Leo I down to our limits.

This work was supported by the Carnegie Institution of
Washington and NSF REU Program Award #0097569.